It has been known for several years that animal and human lymphocytes of one or several different types can be stimulated to become actively cytotoxic to cancer cells ("tumor cells") by incubation in vitro in contact with the corresponding cancer cells, even in circumstances where in vivo contact with the same neoplastic cells ("immunization" or "sensitization") fails to result in such activity. Bringing the lymphocytes and the cancer cells together in tissue culture in vitro for several days bestows specific killing capacity on the lymphocytes. This is sometimes referred to as "education" of the white blood cells.
In most cases normal, allogeneic (individual of same species, but differring genetically) lymphoid cell cultures have been employed but recently allogeneic, syngeneic (individual of the same species and of the same inbred strain) and autologous (cells of the same individual) tumor cells of both rodent and human origin have been utilized as stimulator cells. Kedar et al "In Vitro Induction of Cell-Mediated Immunity to Murine Leukemia Cells. I Optimization of Tissue Culture Conditions for the Generation of the Cytotoxic Lymphocytes", Journal of Immunological Methods, 13, (1976), 1-19, relates to such prior work and is hereby incorporated by reference as indicating the state of the art, particularly with respect to the required culture medium content and other culturing conditions to obtain optimum sensitization of the lymphocytes.